We have continued our studies of chromatin structure ina the neighborhood of expressed genes. The globin gene family in chicken erythroid cells serves as a model system in which it is possible to study the mechanisms associated with regulation of the individual members of the family during erythroid development. We have continued our studies of locus control regions (LCRs) by investigating the generation of hypersensitive sties in the chicken beta globin locus control element. We show that generation of such a site is an all-or-none process, so that partially mutating the site reduces the fraction of sites that is active, rather than reducing athe activity of every site. We have also extended studies of the insulator element at the 5' end of the chicken beta globin locus by showing that activity is distributed throughout the element, but more is contained in a small portion which functions well as an insulator when multiple copies are used. We have extended our studies of the interaction of the erythroid regulatory factor GATA-1 with its target DNA by showing that certain sequences have an unusually high affinity for this factor, suggesting an additional regulatory role. We have also continued studies of the way in which RNA polymerase transcribes through chromatin templates. Using a model system, we have shown that the polymerase is forced to pause in advancing on such templates because of internal DNA loop formation.